The BAA Half has been held for the past nine years on the Sunday of Columbus Day weekend. It may be just as tough to gain entry to as the April 26-miler. For a while there were no qualifying standards and the race is limited to 5,200 entries, which filled in a record 25 hours when registration opened this summer.

It's easy to see why the event is so popular. Coming three weeks before the ING New York City Marathon, it serves as a perfect last long race tuneup for those running that event.

But for the great majority of the entrants, it is a focal goal race, culminating a summer of training for runners not ready to attempt the full marathon distance.

The half marathon is the growth event of the running world, with more of them being created each year than any other distance save 5K.

And like the Boston race, almost all of them are among the most popular, too, filling their fields as fast as organizers can create them.

The BAA Half, held within the shadows of Fenway Park (in its early years, the course actually sent runners through the hallowed Red Sox ballfield, along the warning track beneath the fabled Green Monster) is a home run in almost every aspect.

The prime attraction is the course, which follows the city's Emerald Necklace, a string of urban parks and greenways designed by Frederick Law Olmstead, the landscape architect who also gave us Central Park in New York and Fairmount Park in Philadelphia.

Almost every step of the basically out-and-back layout is surrounded by trees, grass, and spectacular views -- the sight of Jamaica Pond as you crest a hill near four miles, is particularly breathtaking, especially with the early autumn foliage reflecting off its waters.

I mention hills not just in passing; virtually every step of the first 11 miles of the course is either ascending or descending, with Schoolmaster Hill in Franklin Park particularly challenging.

Thankfully, the final topographic change between nine and 11 miles is mostly downhill, although you'll pay for the largess with some sore quads the next day.

Also, beware the last two miles -- the course brings you tantalizingly close to the finish, only to make a large loop past the Museum of Fine Art and around the Fenway itself to obtain the requisite distance.

With just over 4,000 participants actually running, the Half is a relative piece of cake for Dave McGilivray, the marathon race director, and his seasoned crew.

The Fenway staging area is ideal for pre- and post-race activities (the breakfast burritos were a novel and appreciated refueling snack) and is convenient to plenty of parking and mass transit, although the sidewalks got a little crowded this year with the crowds arriving for the noon Sox playoff game.

Brilliant autumn foliage, a beautiful if somewhat challenging course, which includes a stretch through the Franklin Park Zoo near midway, and superb organization make the BAA Half Marathon a must-run race.

But keep your eyes peeled for the opening of registration. While you don't have to run fast to get in as you do for the marathon, if you're not fast at the online registration keyboard, you'll miss out on an event that every New England runner should do at least once.